templates/release: fix path to news.md

Author: bgilbert

.github/ISSUE_TEMPLATE/release.md

@@ -6,5 +6,5 @@
 - [ ] `git clean -dxf && autoreconf -i && ./configure && make distcheck`
 - [ ] Attach release notes to [GitHub release](https://github.com/openslide/openslide-java/releases/new), set pre-release flag, and upload tarballs
 - [ ] [Update openslide-winbuild](https://github.com/openslide/openslide-winbuild/issues/new?labels=release&template=release.md)
-- [ ] Update website: `_data/releases.yaml`, `_includes/news.markdown`
+- [ ] Update website: `_data/releases.yaml`, `_includes/news.md`
 - [ ] Send mail to -announce and -users